Method of making compressed sponges



NOV. 24, 1953 G, HAMMON 2,659,935

METHOD OF MAKING COMPRESSED SPONGES Filed March 18, 1950 Patented Nov.24, 1953 METHOD E MAKING COMPRESSE!) sPoNGES Henry George Hammon,Stevensville, Mich., as-

signor, by mesne assignments, to Christopher L. Wilson, Columbus, Ohio YApplication March 18, 1950, Serial No. 150,418

2 Claims.

This invention relates to a method of making a compressed Spongeparticularly such a sponge comprising polyvinyl formal and in which from35 to 80% oi the hydroxyl groups of the alcohol have been reacted.

In the copending application of Christopher L.

Wilson, Serial No. 29,657, iiled May 27, 1948, now

Y Patent No. 2,609,347 which is a continuation-inpart of applicationSerial No. 769,537, led August 19, 194.7, now abandoned, there iSdescribed and claimed a polyvinyl formal sponge which may be used as anordinary sponge or may be cut in thin sheets to make a synthetic washcloth, chamois skin and the like. These Sponges, as described in theWilson application, are tough and tear resistant and are resistant tothe action of most ordinary chemicals with which they might come incontact. The Sponges have interconnected pores so that they are capableof absorbing and holding a large quantity of water or other liquid.

When the Sponges of the above copending application are dry, they arevery hard and resistant to deformation. However, when they are wet, theybecome quite soft and resilient and can be handled as ordinary Sponges.

'When the Sponges are sold in their normal size and shape they occupy aconsiderable space so that relatively few Sponges can be packaged in anordinary shipping container. The large space ocdried until they are hardthroughout and dry to the touch. The sponge preferably contains not morethan about 2 or 3% water. When the dry Sponge is compressed at apressure suiiicient to reduce materially the bulk of the sponge, thecompressed sponge retains its shape when the pressure is removed anddoes not resume its original shape until it is wet with water. Thepreferred pressure is at least 100 pounds per square inch, althoughpressures up to 1,000 pounds per square inch or more may be employed.This pressure is applied until the sponge has been reduced to athickness of preferably not less than about Il.; its

normal thickness. In actual practice, the Sponges are compressed toabout yf, their normal thickness. The Sponges are compressed preferablyat ordinary room temperatures as an excessive temperature causes theSponges to assume a permanent Set so that they will not recover fullywhen wet. The temperature at which the dry Sponges attain a permanentSet is considerably above normal atmospheric temperatures.

One of the features of this invention is the method of making acompressed polyvinyl formal sponge so that when the pressure is removedthe Sponge will maintain its reduced thickness until the Sponge has beenwet with Water; another feature of the invention is the compressedSponge produced by this method. Other features and advantages of theinvention will be apparent from the following description and theaccompanying drawings. Of the drawings:

Fig. 1 is a fragmentary side elevation of a typical press in openposition with a dry polyvinyl formal Sponge arranged therein; Fig. 2 isa View similar to Fig. 1, but showing the Sponge compressed; and Fig. 3is a perspective view of the compressed sponge.

In the drawings there is illustrated a press having a lower platen I0and an upper platen or ram Il. Arranged between these platens is a poly-Vinyl formal Sponge l2 that has been dried preferably until it containsnot more than about 3% water. -Pressure is applied to the platen l l tocompress the dried sponge until it has, for example, the approximaterelative thickness shown in Fig. 2. When the compressed sponge isremoved from the press, it retains its compressed shape, as shown inFig. 3, until it has been thoroughly wet with water and at which time itimmediately eX- pands until it is Slightly larger than the sponge shownin Fig. 1. The wet sponge is slightly larger than when it is dry as thedrying step itself causes a Slight shrinkage in the sponge.

Although the method illustrated in the drawings shows the sponge beingcompressed through its smallest dimension, it is believed obvious thatthe Sponge could be compressed through any one or more directions.Therefore, when in the Specification and claims the Sponge is said to bereduced in thickness, this is intended to include not only the smallestdimension, but also the largest dimension or any other dimension. Thus,the sponge could be compressed longitudinally of its major axis,laterally of its major axis or in other desired direction.

Having described my invention as related to various embodiments of theSame, it is my inten- 3 tion that the invention be not limited by any ofthe details of description unless otherwise specified, but rather beconstrued broadly Within its spirit and -scope as set out in theaccompanying claims.

I claim:

1. The method of making a compressed sponge which comprises providing apolyvii'iylV formal sponge having interconnected pores throughout,prepared from polyvinyl alcohol and having from 35 to 80% of thehydroxyl groupsof-thealcohol reacted, said sponge containing not moreVthan about 3% Water, and compressing said sponge under a pressuresufcientito.reducefmaterially the bulk of said sponge, saidspongebeingmaintained during the compressing step at a tempera; ture lessI thanthat at which thesponge assumes a permanent set.

2. The method of making a compressed sponge which comprises providing apolyvinyl formal sponge having interconnected pores throughout, preparedfrom polyvinyl alcohol containing tsub-- stantially-no residualhydrolyzablegroups and having from 35 to 80% of the hydroxyl groups ofthe alcohol reacted, said sponge containing not more than about 3%water, and compressing said sponge under a pressure of at least 100pounds per square inch until the sponge has a thickness of not less thanabout one-tenth of its 'original thickness, said spor'igebeingmaintained at lsubs'tar'itially"atmospheric temperature during thecompressing step.

1. THE METHOD OF MAKING A COMPRESSED SPONGE WHICH COMPRISES PROVIDING APOLYVINYL FORMAL SPONGE HAVING INTERCONNECTED PORES THROUGHOUT, PREPAREDFROM POLYVINYL ALCOHOL AND HAVING FROM 35 TO 80% OF THE HYDROXYL GROUPSOF THE ALCOHOL REACTED, SAID SPONGE CONTAINING NOT MORE THAN ABOUT 3%WATER, AND COMPRESSING SAID SPONGE UNDER A PRESSURE SUFFICIENT TO REDUCEMATERIALLY THE BULK OF SAID SPONGE, SAID SPONGE BEING MAINTAINED DURINGTHE COMPRESSING STEP AT A TEMPERATURE LESS THAN THAT AT WHICH THE SPONGEASSUMES A PERMANENT SET.